This invention relates generally to means for shifting a bean or nut grinder between two or more distinct and preselected settings to enable the grinder to grind such beans or nuts to two or more separate particulate sizes as desired, one being a coarse grind setting and the other being at least one fine grind setting. More specifically, the invention relates to a shifting mechanism for a bean or nut grinder employing a pivotal lever arm for moving a rotary grinding burr toward a stationary grinding burr in response to pivoting movement of the lever arm to shift the grinder from a coarse grind setting to at least one fine grind setting.
Generally speaking, such grinders having means for moving a rotary burr toward or away from a stationary burr in order to change the particulate size of the resulting grounds have long been known and used in the prior art. The coffee mill disclosed in U.S. Pat. No. 1,485,855 issued to W. E. Kidney on Mar. 4, 1924 is an early example of such a grinder. The reference grinder includes a housing, a stationary grinding burr attached to a wall of the housing, a drive shaft, a rotary burr slidably keyed to the drive shaft for rotation therewith, and a flanged sleeve surrounding the drive shaft which is movable along the same and engagable with the rotary burr. Also included is a second sleeve surrounding the flanged sleeve and engaging the flange thereof, which is in threadable engagement with the housing, and a hand wheel connected to the second sleeve.
Likewise, the coffee grinders shown in the drawings hereof are typical prior art grinders which include a rotary screw conveyor for transporting coffee beans from a hopper to a grinder consisting of a stationary grinding burr and a linearly movable and rotatable grinding burr attached to an end plate of the screw conveyor. The screw conveyor is keyed to a motor driven drive shaft for rotary motion therewith but is translatable along the latter to adjust the spacing between the grinding burrs. A spring surrounding a portion of the drive shaft and confined between a wall of the housing and the screw conveyor urges the latter forwardly in the housing against a screw threadably connected to an end cap and projecting into the housing against a forward end of the screw conveyor. Upon manual adjustment of the screw, the distance between the burrs can be changed to change the particulate size of coffee to be ground therebetween.
Such prior art grinders, however, do not provide for rapid, precise and automatic adjustment of the spacing between the grinding burrs to permit the obtaining of two or more distinct particulate sizes of ground coffee as is often desired. Manual adjustment of the grinder refinement screw in these prior art grinders is inexact, often requiring time consuming trial and error adjustments each time that a different particulate size is sought. By means of my invention, these and other difficulties encountered using conventionally adjustable coffee grinders are substantially eliminated.